Abstract: In order to compare lime in the traditional process of “limestone calcination-BOF steelmaking” with that in the novel process of “limestone addition for BOF fluxing”, the thermal experience of limestone are described as “low temperature for long time+cooling+high temperature for short time” and “high temperature for short time”, respectively. Limestone lump can be regarded as countless layers. Flake samples were subjected to different thermal experience and the measurement of shrinkage, specific surface area, pore volume and diameter, crystal structure and hydration reactivity to simulate a single layer of lump. The results showed samples calcined at “high temperature for short time” are characterized by low shrinkage, high specific surface area and pore volume, small pore diameter, fine crystal grain size, high crystal distortion ratio and extraordinary high hydration reactivity compared with samples calcined at both “low temperature for long time” and “low temperature for long time+cooling+high temperature for short time”. It can be deduced that the newly generated lime at high temperature in the novel process should be with higher reactivity, which is favorable for the dissolution in slag.

Key words: converter, limestone, lime, slag, reactivity